Generally speaking, the present invention relates to a method of defrosting a cooling unit which includes the steps of providing constant defrost cycle times of predetermined time lengths apart and monitoring openings and closings of a door of the cooling unit to shorten the time lengths in accordance with each of the openings and closings.
A control system for carrying out the method of the invention comprises, in general, defrost means; cam means, constant speed drive means coupled to the cam means, and switch means responsive to the cam means controlling electrical current to the defrost means; and monitoring means coupled to the cam means and responsive to openings and closings of a door of a cooling unit to intermittently advance the cam means so as to shorten time lengths between defrost cycles.
The present invention pertains to a control system for defrosting a cooling unit and more particularly to such a system wherein defrost cycle times are determined by a constant speed timing mechanism.
Present day cooling units, such as refrigerators, utilize timing mechanisms which are driven at a constant speed to provide defrost cycles for the unit. Such mechanisms have a shortcoming in that the defrost cycles provided by a constant speed timing mechanism does not compensate for consumer usage of the refrigerator. More specifically, the constant speed timing mechanism is, for the most part, programmed to provide a constant cycle of 30 minute defrost heater on time following a 51/2 or 111/2 hour compressor run time. The cycle is based on an average usage rate and thus is not sensitive to low or heavy demand periods. Thus, if the refrigerator is used very little and door openings are kept to a minimum, relatively little frost accumulates on the refrigerator coolant coils and thus the defrost heater need not be cycled as frequently. With a defrost heater drawing 1500 watts of power and the associated cool down by the compressor requiring 700 watts, needless energy is consumed.
Accordingly, the present invention is directed to a control system and a method of defrosting a cooling unit such as a refrigerator that relies on the amount of door openings and closings of the refrigerator.